So you also overwrite views in the theme and leave the basic Yii web application skeleton unmodified?
Do you also place your Sass/Compass files into your theme and parse the final CSS there?

I do.
Views and even widgets uses the theme directory.
It's a lot easier to experiment with different themes when everything in 'protected' is agnostic to style.
As for parsing, the Yii app never knows that it was sass/compass which generated the css.

Awesome!
What I really dig is that they finally decided to use Sass - I know that they had a gem, but it was merely a translate of the static css - they didn't take advantage of it.
I already have my own framework based on sass, but I'll definitely use Foundation for a lot of projects now, where a custom framework isn't necessary.

Sometimes font-faced fonts aren't showed (you don't see anything) and I have to make things like rotating the screen or open the "find in page" menu or go back than forward to make them appear... it's like a rendering bug.

I have been a big fan of Bootstrap since I learned of it just a couple months ago. I have already been using Boilerplate since version 2, and lately my designer and I have used Initializr as the base model for all our sites, as it combines Boilerplate and Bootstrap together, allowing us to take advantage of all the best features of Boilerplate - extensive htaccess standardization, superior CSS basis to the old "reset" model, HTML5 support with Modernizr backup - and everything that Bootstrap brings to the table: 12-column grid system, good CSS3 integration, responsive design.

For people concerned about Bootstrap forcing people into a mold, I would point out you can download the code in portions, and remove whatever elements you don't want/like. You could just as easily implement Bootstrap on the Yii level with just e.g. the scaffolding, responsive, maybe some other elements like table and form presentation, navbar/breadcrumbs, dropdown and pagination, as long as you educate full-use Bootstrappers which elements are included and which are left out. Then they could fold the other elements they want back into main.css, or install it as an extension. Or even better, allow the developer to select which elements to install with the Yii application so they know and can control how much of it they want to take advantage of.

One particular reason I would prefer this over the extension method is because of my current experience with Yii-Bootstrap. It's a great extension and I love it, but it highlights the problem with the order in which Yii loads CSS. The extension resources are stored in the assets folder, loaded last by Yii, and override whatever else you have coded except inline styles. So having Bootstrap code as an extension actually gives you FEWER options for customizing your setup.

I'm not necessarily campaigning for its inclusion as opposed to any other framework, but I've been happy enough with it - especially the way Initializr combines it with Boilerplate, that I'd consider it a step up from the implementation of Blueprint in the current version.

Personally, I find that Bootstrap gives me more work because I simply do not like the overall feel of it, and thus have to change it.
The same can be said about Foundation, to a lesser extent, but at least it uses Sass/Compass..